Cleaning device and method for removing a lubricant from the rolls of a roll stand

ABSTRACT

A cleaning device and method remove a lubricant from the rolls of a roll stand. To achieve economical and efficient cleaning of the rolls, the cleaning device includes at least one ultrasonic generator for generating ultrasonic waves, the ultrasonic waves being routed to the surface of the rolls by cleaning water; and a supply line for the cleaning water. The supply line is a branch of a cooling water circuit for the roll stand, enabling the water consumption for the roll stand to be kept constant during the cleaning phase. The water is merely redistributed in that a portion of the cooling water is supplied to the cleaning device. This creates the advantage of the roll temperature rising slightly, with the result that the cleaning performance is supported by the higher roll temperature at which the lubricant is better released from the surface of the roll.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and hereby claims priority to International Application No. PCT/EP2012/075215 filed on Dec. 12, 2012 and European Application No. 12153475 filed on Feb. 1, 2012, the contents of which are hereby incorporated by reference.

BACKGROUND

The invention relates to a cleaning device and a method for removing a lubricant from the rolls of a roll stand.

Roll stands, particularly in hot wide strip mills, typically comprise devices for roll gap lubrication which are usually mounted on the inflow side of the roll stand in the region of the work roll. A lubricant is applied to the work roll, and it is usually a water-oil emulsion that is sprayed on as the lubricant. The lubricant significantly reduces the coefficient of friction between each roll and the material being rolled. In this manner, the rolling forces are reduced and the surface quality of the material being rolled is improved. This has the result that few rolling procedures are required and/or that the profile and flatness of the material being rolled can be better influenced by a greater degree of freedom in respect of the rolling force. Furthermore, the energy usage is reduced and the production spectrum is increased.

However, before the entry of the material being rolled which is, for example, a rolling strip, the rolls, particularly the work rolls must be free from lubricant in order to increase the coefficient of friction of the rolls again since otherwise the risk exists that the material being rolled is not drawn into the roll stand, leading to an interruption of the rolling process. For this reason, shortly before feeding-out of the material being rolled, the roll gap lubrication is switched off and, as a result, the lubricant burns off completely during the remaining roll circulations, due to the high strip temperature. Only following renewed feeding-in of the next material being rolled is the roll gap lubrication switched on again. The head and foot of the material being rolled are therefore rolled unlubricated. However, this has a disadvantageous effect on the rolling process since the foot of the material being rolled which is typically the coldest, requires the greatest rolling force.

From patent application JP 2002-178011-A, it is known to remove the lubricant from the roll in a targeted manner following feeding-out of the previous rolling strip by spraying on warm water under pressure. Depending on the temperature of the water, the water pressure required for this purpose lies between 3 MPa and 15 MPa. The water temperature in this case is at least 50° C. However, a disadvantage in this regard is that the generation of pressure and the heating of the water in order to achieve a good level of effectiveness is very energy-intensive.

From WO 2006/089730 A1, there is known a method for cleaning a metal strip wherein the metal strip is subjected to ultrasonic cleaning in which the metal strip is fed through a container filled with a liquid.

SUMMARY

It is one possible object, during operation of a roll stand, to increase the efficiency during cleaning of the rolls of the roll stand without substantially increasing the water usage for cooling the rolls.

The inventors propose a cleaning device for removing a lubricant from the rolls of a roll stand, wherein the cleaning device comprises at least one ultrasonic generator for generating ultrasonic waves wherein the ultrasonic waves can be conducted, with the aid of cleaning water, to the surface of the rolls, wherein the cleaning device comprises a supply line for the cleaning water, wherein the supply line is a branch of a cooling water circuit for the roll stand.

The inventors also propose a method for removing a lubricant from the rolls of a roll stand, wherein cleaning water is fed to the surface of the rolls and, by the cleaning water, ultrasonic waves are conducted to the surface of the rolls, wherein the cleaning water is diverted from a cooling water circuit for the roll stand.

The advantages disclosed below in respect of the cleaning device and preferred embodiments can be applied accordingly to the method.

The proposals are based on the recognition that the pressure of the cleaning fluid can be reduced, although intensive surface cleaning still takes place with high efficiency in that the cleaning is enhanced with ultrasonic waves which are propagated with the cleaning fluid to the surface of the roll and enhance the cleaning effect. Ultrasound is known for acting also in small indentations in the surface and for mechanically bringing adhering particles or substances into solution. Due to the ultrasonic waves, the danger of damage to the surface of the roll is minimized. In addition, notches in the surface of the roll, for example, fire cracks can be cleaned efficiently. The cleaning fluid is applied to the roll surface, in particular, at a pressure of 5 bar to 15 bar, the pressure being approximately ten times lower than the pressure required according to JP 2002-178011-A. The at least one ultrasonic generator is integrated, in particular, into the cleaning device and is surrounded by the cleaning liquid so that the ultrasonic waves are emitted directly to the cleaning liquid and are propagated therethrough. A liquid bridge is created between the ultrasonic generator and the roll surface which transmits the sound waves. This type of cleaning can be used both for the work rolls and for the backup rolls of a roll stand.

Suitably, water is used as the cleaning agent. Since water is chemically neutral, the use of water is harmless to the rolls. Furthermore, water is widely used in the rolling process, so that large quantities of water are available in a mill train.

The main advantage of this type of cleaning is that the lubrication can be used for the whole strip foot and for a substantial part of the strip head. In this manner, the rolling force is reduced, resulting in a substantial energy saving effect. Furthermore, the product spectrum is thereby extended in that with identical design of the plant (drives, hydraulics and stands), harder steel goods can be rolled.

A particularly good synergy effect which increases the efficiency of the cleaning is achieved in that the cleaning water is diverted from the cooling water circuit for the roll stand, so that the water is conducted via a supply line of the cleaning device and this supply line is a branch of the cooling water circuit for the roll. In particular, in this manner, the water usage for the roll stand can be kept constant during the cleaning phase and there is merely a redistribution of the water in that part of the cooling water is fed to the cleaning device. This results in the advantage that the roll temperature rises somewhat so that the cleaning performance is enhanced by the higher roll temperature, at which the lubricant is better removed from the roll surface.

Preferably, the ultrasonic generator is set to generate ultrasonic waves at a frequency of between 20 kHz and 2 MHz, in particular between 35 kHz and 200 kHz. This frequency range has proved to be particularly advantageous for the ultrasonic cleaning of fine dirt. Suitably, at least two ultrasonic generators with different frequencies are provided, for example, an ultrasonic generator with a frequency of 40 kHz and an ultrasonic generator for 80 kHz.

According to a preferred variant, a sealing element is provided which faces toward a roll gap between the rolls, so that the sealing element seals the roll against outflowing liquid in the direction of rotation of the roll. With the aid of the sealing element, the flow of cleaning water to the material being rolled due to the direction of rotation of the roll, thereby unnecessarily cooling the material being rolled is prevented.

In order to enable the spreading of the cleaning water against the direction of rotation of the roll, an opening facing away from the roll gap is provided at the cleaning device, by which the cleaning water is conveyed to the surface of the roll. It is ensured, through the emergence of the cleaning water against the direction of rotation of the roll, that lubricant removed from the roll surface is not carried away in the direction of rotation of the roll and does not come into contact with the material being rolled.

Preferably, the cleaning device is arranged at least on the inflow side of the respective roll. In a reversible roll stand, cleaning devices can also be provided on the outflow side. Since the cleaning device is distinguished by having a manageable number of additional components, it has a smaller space requirement and can easily be installed in a protected installation position in already existing components of the roll stand. The cleaning device is integrated, in particular, in an insert of the work rolls or in a cooling beam for the roll stand. With regard to a particularly effective surface cleaning, at least one cleaning device is provided on the inflow side per roll and, in the case of reversibly driven roll stands, two cleaning devices per roll are useful—one on the inflow side and one on the outflow side.

According to a further preferred embodiment, the cleaning water contains an emulsifier. With the aid of the emulsifier, the cleaning performance is increased since lubricant particles which are flung upward during the cleaning process cannot so easily become deposited again on the roll surface. In this regard, it is particularly the same emulsifier which is mixed into the lubricant that is used. In this way, it is ensured that no additional operating materials must be made available, rather the cleaning of the roll surface is carried out only with the aid of operating materials which are already required and permitted for the operation of the roll stand.

Suitably, the temperature of the cleaning water is between 0° C. and 70° C. In particular, the temperature of the cleaning water corresponds to an ambient temperature so that no additional heating effort is required for the cleaning water or else that such a heating effort remains within limits.

In order to keep the cleaning time as short as possible, the cleaning device is preferably only active between a discharge of a previous material being rolled by the roll stand and an entry of the following material being rolled. In this way, only the part of the roll which comes into contact with the head of the following material being rolled is cleaned. If the subsequent rolling strip has already been drawn into the roll gap, the cleaning process is interrupted and normal operation of the roll stand is resumed. Particularly during relatively long pauses between two rolling strips, it can occur, however, that the cleaning of the roll surface does not begin with the discharge or that cleaning does not occur continuously until the entry.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the present invention will become more apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a section through a roll stand with ultrasonic cleaning of the work roll,

FIG. 2 is a cross-section through a cleaning device for an upper work roll of the roll stand of FIG. 1,

FIG. 3 is a longitudinal section through the cleaning device of FIG. 2,

FIG. 4 is a coolant circuit and a lubricant circuit of a roll.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

FIG. 1 shows a roll stand 2 which comprises two work rolls 4 and two backup rolls 6. A roll gap 8 is formed between the work rolls, through which gap materials being rolled, in the exemplary embodiment rolling strips, pass. FIG. 1 shows a preceding rolling strip 10 that has previously been rolled and has a reduced thickness, the foot part of which is still situated in the roll gap 8, and a subsequent rolling strip 12 which has been prepared for rolling.

In order to reduce the coefficient of friction between the respective rolling strip 10, 12 and the work rolls 4, a lubricant is fed to the work rolls 4 through lubricant nozzles 14. Before the entry of the subsequent rolling strip 12, however, the roll gap 8 must be lubricant-free so that the rolling strip 12 can be drawn into the roll stand 2 without difficulty. For this purpose, for each work roll 4, a cleaning device 16 is provided, with the help of which a cleaning liquid which, in the exemplary embodiment shown, is water is applied onto the surfaces of the work rolls 4. The cleaning water is applied only to part of the surface. Due to the rotation of the work rolls 4, however, the region of action of the cleaning water is displaced round the circumference of the respective work roll 4 so that finally the whole outer surface of the work rolls 4 is exposed to the cleaning water. Integrated into the cleaning device 16 is an ultrasonic generator 18, with the aid of which ultrasonic waves are generated and are conducted by the water out of the cleaning device 16 to the surface of the work rolls 4. In the exemplary embodiment 16 shown, each cleaning device 16 is built into the cooling circuit of the work rolls 4 and is fastened to a protective sheet 20 on an inflow side. The function of the protective sheet 20 is to prevent cooling water reaching the rolling strip 10, 12.

For each work roll, the coolant circuit has a coolant feed 22 on the inflow side and on the outflow side which opens into a cooling beam 24 and which substantially extends over the length of the working beams perpendicular to the plane of the drawing. Branching from the coolant supply 22 on the inflow side is also a supply line 26 through which water is fed into the cleaning device 16.

The structure of the cleaning device 16 is shown in FIGS. 2 and 3. The cleaning device 16 comprises a hollow space 28 which, during operation, is filled with water. The ultrasonic generator 18 is arranged in the hollow space 28 so that, during operation, water which is conveyed in the direction toward the roller surface, in particular, continuously flows round the ultrasonic generator 18. Arranged on a side 30 of the cleaning device 16 facing toward the roll gap 8 is a sealing element 32 which is configured in the manner of a sealing lip. In particular, by the contact thereof with the roll surface, the sealing element prevents water from flowing downwardly out of the cleaning device 16 to the rolling strip 10, 12 during the rotary motion of the work roll 4. Only at a side 34 of the cleaning device 16 facing away from the roll gap 8 is an opening 36 provided, through which the water is conducted out of the cleaning device 16 to the roll surface in the direction opposing the rotation direction of the work roll 4. In the case of the lower roll 4 (see FIG. 1), the opening 36 faces downwardly so that gravity also acts thereon and reinforces the outflow of the cleaning water. Alternatively or in addition to the apertures 36 facing away from the roll gap 8, apertures (not shown in detail) can also be provided here in the region of the end sides of the work rolls 4. In this case, the lateral outflow of the cleaning water can be collected, for example, via lines or guiding sheets and fed into the circuit.

As shown in FIG. 3, guiding sheets 38 which bring about an even flow through the hollow space 28 are optionally provided in the cleaning device 16, so that the formation of dead zones in the hollow space 28 is prevented.

The water transmits the sound waves from the ultrasonic generator 18 to the roll surface and thereby forms a type of liquid bridge between the ultrasonic generator 18 and the work roll 4. By the ultrasonic waves in the water, the lubricant is atomized at the roll surface and is removed by the water. The water, which is used as cleaning water is conveyed at a pressure of approximately 10 bar to the work roll 4 and has, in particular, a temperature which corresponds to the temperature resulting from the process management and/or the plant state. Thus, in particular, no further heating measures are required for the removal of the lubricant from the roll surface.

The fluid technology-related connection between the cleaning device 16, the cooling water circuit and a lubricant circuit of the roll stand 2 is shown in FIG. 4. The reference sign 40 in FIG. 4 indicates a lubricant tank and the reference sign 42 indicates an emulsifier tank. The lubricant, the emulsifier and water from a water supply line 48 for the stand cooling are brought together in a mixer 44 and fed via a lubricant line 46 to the lubricant nozzle 14 which, in the exemplary embodiment shown, is arranged under the protective sheet 20 close to the roll gap 8.

Cooling water is fed out of the water supply line 48 into the cooling water line 22 and is sprayed via the cooling beam 24 onto the surface of the work roll 4. Part of the cooling water is diverted via the supply line 26 before reaching the cooling beam 24. The ratio of the cooling water flow to the cleaning flow lies in the range of 10:1 to 2:1. The portion of the water in the supply line 26 is mixed in a second mixer 50 with the emulsifier from the emulsifier tank 42 and is subsequently fed into the cleaning device 16. For this purpose, an emulsifier line 52 leads directly from the emulsifier tank 42 to the second mixer 50 which, like the cleaning device 16, is also arranged on the protective sheet 20. The efficiency of the cleaning water is increased by the emulsifier. The supply line 26 also opens into the second mixer 50.

The cooling water and the cleaning water, which runs laterally off the work roll 4, is finally collected in a cooling water sump 54 and is conducted out of the roll stand 2 for processing.

It is a characteristic of the cooling water circuit of FIG. 4 that, with the aid of the valves 56 a and 56 b, the water feed into the lines 22 and 26 can be controlled dynamically and in a short time span depending on the rolling process. For example, during the rolling of the preceding rolling strip 10, the water supply to the cleaning device 16 is interrupted so that the whole quantity of water is used in the cooling water line 22 for cooling purposes. The cleaning device 16 is switched on only briefly between a discharge of the preceding rolling strip 10 and an entry of the subsequent rolling strip 12. For this purpose, part of the water in the cooling water line 22 is diverted into the supply line 26 and finally reaches the cleaning device 16. In particular, for as long as the cleaning device 16 is active, less water flows to the roll surface, at least from the cooling beam 24 on the inflow side. However, this has the positive side-effect that through the heating of the roll surface, the lubricant is more easily removed.

Overall, both during the rolling of the rolling strip 10 and also between the discharge and the subsequent entry of the new rolling strip 12, despite the cleaning of the roll surface with cooling water, the same quantity of cooling water is used. The roll stand 2 is therefore distinguished not only by an efficient operation thanks to the increase in the coefficient of friction during feeding in of the rolling strips 10, 12, but also by a minimized energy requirement and a potentially constant water requirement.

The invention has been described in detail with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention covered by the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in Superguide v. DIRECTV, 69 USPQ2d 1865 (Fed. Cir. 2004). 

1-16. (canceled)
 17. A cleaning device for removing a lubricant from rolls of a roll stand, the cleaning device comprising: a hollow space configured to receive cleaning water from a water supply line of a cooling water circuit for the roll stand and to apply the cleaning water to a surface of at least one of the rolls; at least one ultrasonic generator configured to generate ultrasonic waves in the cleaning water such that the ultrasonic waves are transmitted via the cleaning water to the surface of the at least one roll.
 18. The cleaning device as claimed in claim 17, wherein the at least one ultrasonic generator is configured to generate ultrasonic waves at a frequency of between 20 kHz and 2 MHz.
 19. The cleaning device as claimed in claim 17, further comprising a sealing element that faces a roll gap between the rolls and that is configured to prevent the cleaning water from flowing into the roll gap.
 20. The cleaning device as claimed in claim 19, wherein an aperture is provided for allowing the cleaning water to be applied to the surface of the at least one roll, the aperture facing away from the roll gap.
 21. The cleaning device as claimed in claim 17, wherein the cleaning device is arranged on an inflow side of the at least one roll.
 22. The cleaning device as claimed in claim 17, wherein the cleaning water contains an emulsifier.
 23. The cleaning device as claimed in claim 17, wherein a temperature of the cleaning water is between 0° C. and 70° C.
 24. The cleaning device as claimed in claim 17, wherein the cleaning water is applied to the surface of the at least one roll only between a time when a previous roll strip has been discharged from a roll gap between the rolls and a time when a subsequent roll strip has been entered into the roll gap.
 25. The cleaning device as claimed in claim 17, wherein the at least one ultrasonic generator is configured to generate ultrasonic waves at a frequency of between 35 kHz and 200 kHz.
 26. A method for removing a lubricant from rolls of a roll stand, the method comprising: generating ultrasonic waves in cleaning water, the cleaning water being supplied from a supply line that is branched from a cooling water circuit for the roll stand; and transmitting the ultrasonic waves to the rolls by applying the cleaning water to surfaces of the rolls.
 27. The method as claimed in claim 26, wherein a frequency of the ultrasonic waves is set at between 20 kHz and 2 MHz.
 28. The method as claimed in claim 26, wherein a sealing element is provided to prevent an outflow of the cleaning water in a direction of rotation of at least one of the rolls.
 29. The method as claimed in claim 26, wherein the cleaning water is applied to the surfaces of the rolls through apertures in a cleaning device, the apertures facing away from a roll gap that is provided between the rolls.
 30. The method as claimed in claim 29, wherein the cleaning device is arranged at an inflow side of the rolls.
 31. The method as claimed in claim 26, further comprising mixing an emulsifier into the cleaning water.
 32. The method as claimed in claim 26, wherein the temperature of the cleaning water is set to between 0° C. and 70° C.
 33. The method as claimed in claim 29, wherein the cleaning water is applied to the surfaces of the rolls only between a time when a previous roll strip has been discharged from the roll gap and a time when a subsequent roll strip has been entered into the roll gap.
 34. The method as claimed in claim 26, wherein a frequency of the ultrasonic waves is set at between 35 kHz and 200 kHz.
 35. A cleaning system for removing a lubricant from rolls of a roll stand, the cleaning system comprising: a cooling water circuit configured to supply cooling water to the rolls; a cleaning device configured to receive cleaning water that is supplied to the cleaning device from a supply line that is branched from the cooling water circuit and to apply the cleaning water to surfaces of the rolls; and at least one ultrasonic generator configured to generate ultrasonic waves in the cleaning water, the ultrasonic waves being transmitted to the surfaces of the rolls via the cleaning water. 